This invention relates to a process for preparing linearly-extended polyalkylenepolyamines, such as diethylenetriamine and linear and branched triethylenetetramines. Linearly-extended polyalkylenepolyamines also include alcohol-extended piperazines, such as N-(2-hydroxyethyl)piperazine, and amine-extended piperazines, such as N-(2-aminoethyl)-piperazine.
Linearly-extended polyalkylenepolyamines find utility as dispersants, surfactants, chelants, catalysts, curing agents, and extenders in polyurethanes. In addition, linearly-extended polyalkylenepolyamines are useful starting materials or intermediates in the preparation of pesticides, veterinary antihelmintic pharmaceuticals, and high temperature lubricating oils.
It is known that non-cyclic polyalkylenepolyamines can be prepared by the reaction of an alkyl halide with ammonia or an amine. The product is a polyalkylenepolyamine hydrohalide salt, which must be neutralized with base in order to recover the valuable polyalkylenepolyamine product. The neutralization produces a waste stream of metal salt, which must be removed. Moreover, the process produces considerable amounts of undesirable cyclic compounds.
It is known that salt-free linear polyethylenepolyamines can be prepared directly by reacting an ethanolamine with an ethyleneamine in the presence of hydrogen and a hydrogenation catalyst. For example, U.S. Pat. No. 3,714,259 discloses such a process with preferred catalysts derived from the oxides of chromium, copper, nickel, and cobalt. Likewise, U.S. Pat. No. 3,270,059 teaches a process for production of diaminoalkanes comprising passing a mixture of alkanediols or alkanolamines, ammonia, and hydrogen over a catalyst containing at least one metal sensitive to sulfur or sulfur compounds. Preferably, the metal is a metal from Groups IB or VIII, including copper, silver, iron, nickel and cobalt. Optionally, promoters such as compounds of Group VIB elements can be employed. These processes produce substantial quantities of undesirable cyclic products, such as piperazine. Moreover, these catalysts require large amounts of hydrogen to maintain the catalytic activity.
U.S. Pat. No. 4,206,150 teaches the amination of aliphatic diols with ammonia or primary or secondary amines, preferably, containing one amine group. The process is conducted in the presence of a catalyst containing a mixture of components selected from the group consisting of copper, copper oxide, and mixtures thereof, and molybdenum oxide, tungsten oxide, and mixtures thereof. This process requires on a mole basis more copper than molybdenum or tungsten, and favors use of hydrogen to maintain the catalyst's activity.
It would be advantageous to have a process for the direct amination of aliphatic alcohols to polyalkylenepolyamines which does not require large amounts of hydrogen and expensive metals. It would be more advantageous if such a process produces high selectivity for linearly-extended products and low selectivity for undesirable cyclic materials. It would be most advantageous if the catalyst for such a process is insoluble in the presence of amines and retains its physical integrity in the presence of water. Such a process would eliminate the need for neutralizing hydrohalide salts and disposing of a waste salt stream. Moreover, in such a process the problems of catalyst leaching, reactor plugging, and catalyst separation would be avoided. Accordingly, the combined aforementioned advantages would render the amination process suitable for industrial applications.